1. Field of the Invention
This invention relates to guide bars for chain saws and in particular it relates to a guide bar having a nose sprocket that operates in a manner to receive a lubricating fluid and direct the fluid into and through the nose sprocket bearings.
2. Background of the Invention
Whereas the invention is beneficial to chain saws in general, it is particularly beneficial for aggregate cutting chain saws. Chain saws utilized to produce cuts in hard materials such as rock, stone, concrete and the like are subjected to very abrasive conditions. Lubrication is a major consideration and the invention provides improved lubrication.
Typically chain saws as contemplated herein have a power head with a drive sprocket, a guide bar for guiding an endless chain, and an endless chain. The guide bar is mounted to the power head in relation to the drive sprocket and the endless chain is entrained around the guide bar and drive sprocket. The chain is guided around the outer or nose end of the bar by an idling sprocket. This sprocket is referred to as a nose sprocket and the bar a sprocket nose bar.
The chain is an articulated chain having center drive links interconnected by pairs of side links. The center links have depending tangs that are engaged by the drive sprocket to propel the chain around the bar. The saw chain has special cutting elements mounted to certain of the links for producing a cut. Most often the cutting elements (for cutting abrasive materials) are a very hard material, such as industrial grade diamonds, embedded in a matrix.
As a cut is produced, the aggregate material is removed in the form of fine particles or fines that are very abrasive and cause rapid wearing when lodged between bearing surfaces. It is thus necessary to remove, or preferably to prevent entry of the particles between the bearing surfaces, i.e., between the components of the saw that move relative to each other such as the guide rails of the bar and the saw chain.
The guide bar is provided with an array of channels provided within the bar for transmitting a flushing, cooling and lubricating fluid to the guide grooves of the bar. Rather than a single opening to the guide groove, as is common in other applications, multiple ports are provided to the groove permitting a high volume of fluid to be dispensed along the length of the bar. The high volume of the fluid dispensed to the guide groove through the multiple ports will flush away any of the fines that enter between the chain and the rails, will cool the guide bar and chain and provide a lubrication of the guide bar and chain.
It is also desirable to flush out and lubricate the bearing surfaces of the nose sprocket. There is, however, a problem in providing fluid flow to the sprocket nose bearing. The nose sprocket is rotatably mounted in the nose end of the bar and is of course rotating during the cutting action. The rotating action of the sprocket inherently repels the fluid directed at its periphery which makes it difficult to provide fluid flow to the bearing at the center of the nose sprocket. It is thus not adequate merely to provide a fluid flow to the nose end of the guide bar.